Antimicrobial Stewardship Programs: Effects on Clinical and Economic Outcomes and Future Directions

Improving the use of antimicrobial agents should limit collateral damage associated with their use (eg, damage to normal flora and increased resistance), and ideally infections should be better managed. As previously mentioned, one of the concerns with antibiotic usage (particularly fluoroquinolones, macrolides, and broad-spectrum agents) is that collateral damage could lead to increased rates of C. difficile infection. One meta-analysis showed no significant reduction in the rate of C. difficile infection (as well as overall infection rate) relative to ASPs [22]; however, this finding was based on only 3 of the 26 studies analyzed, and only 1 of those 3 studies utilized restrictions for flouroquinolones and cephalosporins. An interrupted time series (ITS) study similarly found no significant reduction in C. difficile infection rate [32]; however, this study was conducted in a hospital with low baseline antibiotic prescribing (it was ranked second-to-last in terms of antibiotic usage among its peer institutions), inherently limiting the risk of C. difficile infection among patients in the pre-ASP setting. In contrast to these findings, a meta-analysis specifically designed to assess the incidence of C. difficile infection relative to stewardship programs found a significantly reduced risk of infection based on 16 studies (RR 0.48, 95% CI 0.38–0.62, P < 0.001; I ² = 76%) [41], and the systematic review conducted by Filice et al [24] found a significant benefit with regard to the C. difficile infection rate in 4 of 6 studies. These results are consistent with those presented as evidence for the impact of stewardship on C. difficile infection by the CDC [42]. Aside from C. difficile infection, one retrospective observational study found that the 14-day reinfection rate (ie, reinfection with the same infection at the same anatomical location) was significantly reduced following stewardship intervention (0% vs. 10%, P = 0.009) [29]. This finding, combined with the C. difficile infection examples, provide evidence for better infection management of ASPs.

While the general trend seems to suggest mixed or no significant benefit for several clinical outcomes, it is important to note that variation in outcomes could be due to differences in the types of ASP interventions and intervention study periods across differing programs. Davey et al [37] found variation in prescribing outcomes based on whether restrictive (ie, restrict prescriber freedom with antimicrobials) or persuasive (ie, suggest changes to prescriber) interventions were used, and on the timeframe in which they were used. At one month into an ASP, restrictive interventions resulted in better prescribing practices relative to persuasive interventions based on 27 studies (effect size 32.0%, 95% CI 2.5%–61.4%), but by 6 months the 2 were not statistically different (effect size 10.1%, 95% CI –47.5% to 66.0%). At 12 and 24 months, persuasive interventions demonstrated greater effects on prescribing outcomes, but these were not significant. These findings provide evidence that different study timeframes can impact ASP practices differently (and these already vary widely in the literature). Considering the variety of ASP interventions employed across the different studies, these factors almost certainly impact the reported antimicrobial consumption rates and outcomes to different degrees as a consequence. A high degree of heterogeneity among an analyzed dataset could itself be the reason for net non-significance within single systematic reviews and meta-analyses.